Increased Safety 'e'

Background

This protection prevents sparks or any exceeding surface temperature from occurring in abnormal and normal situations for which the motor is certified.

The EHSRs of ATEX Directed corresponding to Category 2 must be followed:

• Potential ignition sources such as sparks, flame, electric arc and other ignition sources must not occur.
• Stray electric and leakage currents in conductive equipment parts which could result must be prevented.

To be installed in Zone 1, the motor must comply with Category 2 requirements even though used in Zone 2.

The explosive gas penetrates inside the motor without any risks of explosion because:

• All parts inside the motor do not exceed the temperature class for which the motor is approved
• In abnormal situation the motor is switch off before the inside temperature reached the temperature class of motor
• No risks at all that sparks occur due to the material selected for the relevant components, specific design regarding connection and clearances of moving parts.

Standards concerned with the protection type 'e':
EN 60079-0: 2004-03	Electrical apparatus for explosive gas atmospheres. Part 0: General requirements.
EN 60079-7: 2003-08	Electrical apparatus for explosive gas atmospheres. Part 7: Increased safety 'e'.
EN 50014: June 1997	Electrical apparatus for potentially explosive atmospheres. General requirements.
EN 50019: July 2000	Electrical apparatus for potentially explosive atmospheres. Increased safety 'e'.
IEC 60079-0: 2004-01	Electrical apparatus for explosive gas atmospheres. Part 0: General requirements.
IEC 60079-7: 2001-11	Electrical apparatus for explosive gas atmospheres. Part 7: Increased safety 'e'.
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In addition to the standards above there is in Germany a recommendation for the minimum tE time under the reference VIK: März 1999.
This protection is defined by:

• Temperature class
• t_E: The maximum locked rotor time allowed for the motor and used to set up the "e" certified relay which protects the motor.

This protection is ensured during normal running condition, in inferior conditions and in abnormal conditions in case of a rotor situation occurring after a continuous running period.

Temperature rise:
The maximum t_E time to provide a compatibility with the relay for trip off should follow the minimum value defined by the standards for increased safety motors.